1. Field of the Invention
The present invention relates to an organic light emitting display and a method of driving the same.
2. Description of Related Art
Recently, there have been various types of flat panel display devices with reduced weight and volume in comparison to cathode ray tube display devices. The flat panel display devices can be categorized as a liquid crystal display, a field emission display, a plasma display panel, an organic light emitting display, and the like.
Among these flat panel display devices, the organic light emitting display displays images using organic light emitting diodes (OLEDs) that emit light through the recombination of electrons and holes. The organic light emitting display device has a fast response speed and a low power consumption.
Generally, pixels of an organic light emitting display device display images by charging a predetermined voltage in a storage capacitor included in each of the pixels and supplying a current corresponding to the charged voltage to an OLED (an analog driving manner). However, in such a driving method (or manner), there is a limit to the number of gray levels because expressing a large number of gray levels requires the use of a large number of different voltages stored in the storage capacitor. Further, it is difficult to display a uniform image due to variations on the threshold voltage and mobility of a driving transistor included in each of the pixels.
In order to solve these problems, there has been proposed a digital driving manner. In the digital driving manner, a data signal corresponding to turn-on or turn-off is supplied to each pixel, and turn-on times of the pixels are controlled during a plurality of sub-frame periods included in one frame, thereby expressing a gray level. However, in the digital driving manner, a gray level is expressed according to a light emitting time of the pixels. For this reason, false contour noise is generated while a moving image is displayed.
In order to reduce such false contour noise, a method of driving even-numbered and odd-numbered scan lines at a time difference of ½ frame has been proposed in Korean Patent Application No. 2006-0110571. In Korean Patent Application No. 2006-0110571, when pixels coupled to the even-numbered scan lines are driven, pixels coupled to the odd-numbered scan lines are then driven after ½ frame. As such, if the pixels coupled to the even-numbered and odd-numbered scan lines are driven at a time difference of ½ frame, images having different weight values are displayed between adjacent lines. Accordingly, false contour noise can be reduced without an increase in number of sub-frames.
However, when the pixels coupled to the even-numbered and odd-numbered scan lines are driven at a time difference of ½ frame, line-shaped noise may be additionally generated.